Arthur Strahler’s Climatic Classification: Types and Zones
Bolivarian Republic of Venezuela
Ministry of Popular Power for Education
UEP “Menca Leoni”
Palo Black-Edo. Aragua
Members:
Teacher: Anahis Latouche
Danny Becerra, Andrea Leal
Geography of Venezuela, Charles Rangel
Joseph D. Benitez
Oscar Espinoza
Rosa Gomez
Vicente Hurtado
Sylvana Carmona
9th Grade “U”
February 2009
CLIMATIC CLASSIFICATION OF ARTHUR STRAHLER
This classification reflects the need to take into account seasonal variations in climate throughout the year, i.e., the succession of types of weather that occur over a territory. It also considers the action centers acting as air masses causing these types of weather.
This classification has the advantage that it can relate to the classification of large terrestrial biocenosis. With this, we may be able to cross the climatic and biogeographic classifications to account for the vegetation and animal species present on the surface of the earth and its relation to climate.
TYPES OF CLIMATE BY ARTHUR STRAHLER
Wet equatorial climate (Equatorial)
This is the climate in the intertropical convergence zone (ITCZ), around 10 degrees of latitude around the Equator. It is dominated by warm, humid equatorial air masses, but we also find maritime tropical air masses. It’s a rainy climate throughout the year; the rains are usually strong and of a convective character. It exceeds 2,500 mm per year. There may be some drier periods due to the displacement of the ITCZ. Throughout the year, we find a remarkable thermal uniformity, around 27 º C. Koeppen classification in Af.
The representative areas are the Amazon Basin and Congo (Africa), and the East Indies, from Sumatra to New Guinea.
Monsoon climate and trade winds along the coast (Monsoon)
This is a climate that is between the 5th and the 25th degree of latitude. It is dominated by maritime tropical air masses, warm and damp, coming from the western edge of the subtropical anticyclones. It has a very marked dry season, and a maximum rainfall is reached when the ITCZ is near. It tends to occur in the east of the continents and is enhanced when there is an orographic barrier that forces air masses to rise. It’s a very rainy climate, around 2500 mm, with little temperature fluctuation, between 25 and 27 º C. In the Koeppen classification, Am and Af.
The most representative areas of this kind of weather are: Southeast Asia, the North Florida area and the Gulf of Mexico, Central America and the Caribbean, and Madagascar in Africa.
Dry and humid tropical climate (Tropical)
This climate is found between 5 ° and 20 ° latitude (10 º and 30 º in Asia). The action centers are: the ITCZ and subtropical high pressure. Air masses that affect it are equatorial and tropical maritime and continental. It is characterized by two marked seasons: a dry and a wet one. The dry season is when the sun is low on the horizon at noon, and the wet one is when it is high. The rains depend on the position of the ITCZ. In the Koeppen classification, Aw and Cw.
The representative areas of these climates are: India, Indochina, western Africa, South America in the peripheral regions of the Amazon, and Australia.
Dry tropical climate (desert)
This climate is found between 15 º and 25 º latitude. It occupies regions of the continental tropical air masses, i.e., the cells of the high pressures. Air masses are stable and dry, and the sunshine is strong. The temperature cycle depends on the relative position of the sun. It contains the arid and hyper-arid, but in transition areas, there are some months when it rains. The daily thermal amplitude is very contrasting, but not the annual. They tend to be high winds that hinder plant colonization. In the Koeppen classification, BWh and BSH.
The representative areas are the Sahara in Africa, Arabia, the Australian desert, and small regions of South Africa, South America, and Mexico.
Subtropical dry (desert)
This climate is between 25 º and 35 º latitude. It is essentially a northward extension of the dry tropical climate, but rainfall is greater, and the annual temperature range is as well. It is dominated by the continental tropical air masses, but at times when the relative position of the sun is low, it can reach continental polar air masses or sea. In the Koeppen classification, BWh and BSH.
The typical areas of this climate are: the deserts of South America, North Africa, the Middle East, the southern regions of Australia and South Africa, and the Argentine Pampas and Patagonia.
Humid subtropical climate (Chinese)
This climate is between 20 degrees and 35 degrees latitude and occurs on the eastern facade of the continents. It is dominated by maritime tropical air masses, warm and humid, that arise in the western sector of the subtropical anticyclones, but also reach continental polar air masses, cold and dry, with variations of the polar front. It is really a northward extension of the monsoon climate and trade winds along the coast, but with polar air advection. The marine character of tropical air masses causes heavy rainfall in summer, mostly of a convective type. Hurricanes are frequent in autumn. In the Koeppen classification, Cfa.
The representative climate zones are: the southeastern U.S., southern China, Formosa (Taiwan) and Japan, Uruguay and neighboring areas of Brazil and Argentina, and the east coast of Australia.
Mediterranean climate
The Mediterranean climate is between 30 degrees and 45 degrees latitude and west of the continents. It is characterized by relatively wet winters and dry summers, due to changes of the polar front and subtropical high pressures. These are the main action centers that dominate the climate. Air masses that we find are of a continental tropical and maritime polar or maritime nature. The maritime polar air masses dominate in autumn, winter, and spring. They are responsible for most of the rainfall in this climate. The rainy seasons are the intermediate fall and spring. Especially in autumn, there might be heavy rains caused by the accumulation of heat in bodies of water during the summer and the arrival of cold polar drops. In winter, thermal anticyclones may occur locally. Temperatures are mild throughout the year, with a low annual temperature range (about 15 º C). However, the topographic conditions may vary these parameters and find a drier climate and cold dry winters and cool summers and cold, but always within the general conditions. The most significant climate feature is three to five months of dryness in the summer, when under the dominion of the subtropical anticyclone. Koeppen classification into the CSA and CSB.
The representative climate zones are: the Mediterranean environment of Europe and Africa, Central and South America California, southwestern Australia, the Chilean coast in the vicinity of Santiago, and the Cape Town region.
Maritime climate of the west coast (or Atlantic Ocean)
This climate is between 35 degrees and 60 degrees latitude, on the western coasts of continents. It is dominated by action centers of the polar front and subtropical high pressure. The air masses that dominate are polar sea, which brings the polar front, cold and wet. The action of the subtropical anticyclone is reduced to a few days in summer, which is the season with less rain. The rest of the year, rainfall is abundant, although rainfall peaks in winter. Temperatures are cool but soft and with low thermal amplitude. In the Koeppen classification, Csb and Cfb.
They are representative of this climate zones: Europe, the U.S. West Coast, New Zealand, and Chile.
Dry climate of middle latitudes (Mainland)
This climate is developed between 35 º and 55 º latitude in the interior of large landmasses, away from the influence of maritime polar air masses. It is also affected by fluctuations of the polar front, but the air masses that dominate, almost exclusively, are the continental polar, cold and dry. In winter, it is under the sway of a powerful cyclone heat source of continental polar air masses, which also operates in summer. The rains are sporadic and are caused by the advection of maritime polar air occasionally, which may occur in summer. Summer is the rainy season. However, this climate is dry. The winters are cold and harsh, and summers can be hot. The annual temperature range is very marked, and may also be daily. In the Koeppen classification, BWk and BSk.
The representative areas of this climate are almost exclusively the Northern Hemisphere: the central regions of North America, Europe, and Asia.
Humid continental climate (Continental)
This climate is between 30 º and 35 º latitude in the east and west of the continents, though hardly found in the southern hemisphere. In reality, it is the transition between the maritime climate of the west coast (or the humid subtropical climate) and the dry climate of the mid-latitudes. It is in the area of activity of the polar front as they affect the masses of continental polar and arctic air, but also tropical sea, which are responsible for most of the rains, the monsoon effect. In Europe, these air masses are of polar sea. The rain is heavy, and temperatures are cold and contrasted. You can have hot and rainy summers and cold and relatively dry winters. This tremendous temperature oscillation is due to the advection of air masses of tropical and arctic origin. Koeppen classification into the DFA and DFB.
The representative climate zones are the eastern U.S. and southern Canada, eastern China, Korea and Japan, and Central and Eastern Europe.
Climates of the boreal forests (Boreal)
This climate is found between 50 º and 70 º latitude, mostly north, as the southern hemisphere is only found in certain islands. It occupies regions of continental polar air masses that feed the polar front. The winters are long and harsh, and summers are short and cool. In winter, air masses reach the Arctic, and polar sea in summer. Summer is the rainy season. But overall, the rains are few and almost always in the form of snow. In the Koppen classification, Dfc, Dw, and Cfc.
The most typical regions of this climate are: Eurasia from northern Europe to the Pacific, Siberia, and North America from Alaska to Greenland.
Tundra climate
This climate is developed between 60 º and 75 º latitude. Occupying the Arctic and Antarctic coastal fringes, it is dominated by continental polar air masses and sea and Arctic air masses. There are frequent cyclonic storms. The winters are long and harsh. There is no real summer, although a station, very short, is somewhat softer. The rain is always in the form of snow. In the Koppen classification, ET.
The countries representative of this climate are: the Arctic slope of North America, Europe and Siberia, the coast of Greenland, and the Antarctic coast.
Climate of the polar cap (Polar)
This climate is developed between 65 º and 90 º latitude. They are air source regions of Arctic and Antarctic air masses. It is situated in the ice sheets and has very low temperatures all year round, always below 0 º C, which causes a decrease in thermal and air causes a strong temperature inversion. There are strong surface winds. Rainfall is low but always as snow, which melts. In the Koppen classification, EF.
The regions typical of this climate are the Arctic and Antarctic ice caps and ice sheets of Greenland.
The biocenosis is virtually impossible; there is no soil or vegetation, or wildlife, except bacteriological.
Mountain Climates
The mountains tend to have different climatic conditions from the climate zone where they are, due to a decrease in temperature with height. The negative temperature gradient of 0.5-1 ° C per 100 m represents an increase in relative humidity and the presence of abundant orographic rainfall on the windward side and less on the leeward side. The orientation with respect to the prevailing winds and the sun is of vital significance. They also receive more sunshine and specific wind patterns, creating a differential topoclimate. However, the action centers, air masses, and fronts that affect it are the same as in the zonal climate.
The effect of these differences in temperature and humidity is momentous in the altitudinal distribution of vegetation. In a cliserie, four floors are usually differentiated: basal, montane, subalpine, and alpine at different heights and with different thicknesses depending on the different mountains and guidance. In reality, cliserie is the replacement of a plant community by another due to a change in weather conditions. It may occur in the same place over time, or by introducing changes in climate at the altitude of a mountain. Formerly, it was called climaserie.
The mountain climate is especially important in Europe. Although not very high mountains, they are very humane and mountains of great economic and ecological importance.
In a Mediterranean mountain, for example, can be found in cliserie: Mediterranean forests, in the basement floor; oak, in the montane zone; hardwood forest in the subalpine; and alpine meadows in coniferous and the alpine. This fact led many geographers and naturalists to believe that the observable climate in height, on a mountain, was a local reflection of latitudinal climatic variety. However, this is not true. Keep in mind that some morphogenetic processes interfering with the other floors, especially in the lower ones, remove the traces of these grades. What does seem to be observed is that the drop in temperature and humidity increased with height in the cliserie causes are represented progressively less thermophilic species and increased demands for water that allows the zonal biocenosis found mountain enclave. But also the species adapted to the worst soils, since the slope generates phenomena of migration of colloids, impoverishing soil in height.
The mountains are in transition climates, or between two biocenosis, present in both species cliserie biocoenosis, and soils are generally oriented to spread sunshine and shade. It is the typical case of the Mediterranean mountains.
It is also true that past climate changes entailed a different distribution of biocoenosis and were able to stay, residually, in the mountain sites that are more favorable, a biocoenosis enclaves elsewhere. These enclaves remain precariously feeding on themselves, and a slight degradation of the environment can make them disappear beyond recovery.
CLASSIFICATION BIOCLIMATIC HOLDRIDGE
It differs from other classifications in climate or vegetation that quantitatively define the relationship in the natural order among the major factors of climate and vegetation. Climatic factors considered are the bio-temperature, precipitation, and humidity. Biotic factors, dependent on weather, are the features, complexity, and biological forms of the natural community.
Holdridge called “life zones” to their bioclimatic units to highlight the fact that climate-related biotic elements include both the natural vegetation and wildlife. This vegetation is used in Venezuela.
In Venezuela, 19 areas of life have been identified:
- Montane rain forest
- Lower Montane Rain Forest
- Rain Forest premontane
- Tropical Rain Forest
- Very humid montane forest
- Very wet lower montane forest
- Very humid forest
- Tropical dry forest
- Rain Forest premontane
- Montane rainforest
- Lower Montane Rain Forest
- Lower Montane Dry Forest
- Dry Forest premontane
- Tropical dry forest
- Tropical desert scrub
- Thorny Monte premontane
- Monte Thorny tropical
- Monte tropical wet